Posttraumatic stress disorder (PTSD) is one of the most frequently co-occurring disorders in persons seeking treatment for alcohol dependence (AD). Despite the high level of comorbidity between these disorders, there are (a) few controlled trials testing whether concurrent treatment of the two conditions improves AD outcomes, and (b) few laboratory-based studies directed at understanding the mechanisms by which PTSD may affect AD-PTSD treatment outcome. One possible mechanism may be the negative emotions experienced by individuals with PTSD when remembering aspects of a traumatic event. Laboratory-based research conducted by this team of investigators has shown that when exposed to an imaginal trauma cue, individuals with DPTSD report increases in negative emotion and alcohol craving and that this trauma-related negative emotion and alcohol craving can be decreased with trauma-focused prolonged exposure. In the treatment literature there is growing evidence that trauma-focused exposure therapy may benefit AD-PTSD individuals, however, longer-term AD treatment outcomes have not been reported from AD-PTSD treatment trials. Despite the promising preliminary data that has been reported, a significant problem in past substance abuse-PTSD treatment studies has been subject retention. To address this issue, the current application proposes to use a well established therapeutic approach (i.e., motivation enhancement therapy) to increase study retention. Therefore, to build on previous work conducted by the research team, it is proposed that a randomized, controlled clinical trial of prolonged exposure for PTSD be conducted in a sample of AD-PTSD treatment seekers. The clinical trial will incorporate two laboratory sessions (pre and post-treatment) intended to assess change in trauma-related negative emotion and alcohol craving. In addition, the study will assess if reductions in PTSD symptom severity lead to improved AD treatment outcomes at 3 and 6-month follow up. Moreover, we propose to implement a trauma-focused MET session, to test if retention during AD-PTSD treatment can be improved. Success in demonstrating that a reduction in emotional reactivity to trauma cues results in better AD treatment outcomes and that a brief MET session increases study retention will provide strong support for the use of exposure-based approaches to treat comorbid ADPTSD and could markedly improve AD treatment outcomes for this population.